1. Technical Field
The embodiments herein generally relate to semiconductor processing and characterization, and more specifically, to an improved system and method for uniformity testing of semiconductor substrates.
2. Description of the Related Art
The ability to process uniformly across a monolithic substrate and/or across a series of monolithic substrates is advantageous for manufacturing efficiency and cost effectiveness, as well as repeatability and control. However, uniform processing across an entire substrate can be disadvantageous when optimizing, qualifying or investigating new materials, new processes, and/or new process sequence integration schemes, since the entire substrate is nominally made the same using the same materials, processes, and process sequence integration schemes. Each processed substrate generally represents, in essence, only one possible variation per substrate. Thus, the full wafer uniform processing under conventional processing techniques results in fewer data points per substrate, longer times to accumulate a wide variety of data, and higher costs associated with obtaining such data.
For example, characterizing graphene (e.g., characterizing graphene uniformity) is an important, yet time consuming using conventional systems. For example, one conventional system for characterizing graphene includes atomic force microscopy (AFM). Conventional uses of AFM to characterize graphene, however, typically suffer from a low throughput, are time-consuming characterization methods, and could damage the sample during testing. Conventional systems also use ellipsometry, and optical microscopy to characterize graphene. For ellipsometry, to determine the graphene thickness, optical properties (refractive index and absorption constant) for each sample typically must be known first, which is a time-consuming process when testing multiple samples because the optical properties may change from sample to sample. In addition, the optical response for very thin films (e.g., <20 Å) is often buried in noise. For optical microscopy, the contrast of graphene films generally has to be optimized for characterization by adjusting the underlying dielectric material, thickness, and the light wavelength used, which is also a time-consuming process. Due to the time-consuming and destructive nature of conventional systems, a wafer can generally only be used to evaluate a single process condition using conventional technology. Generally, the unit processes and test workflows (e.g., combinatorial workflows) used in current industry are complicated, time-consuming, and not cost efficient when using conventional technologies. For example, to know the result of each condition, one wafer with many follow-up steps is required, which under current technology is very complicated as well as cost inefficient. In particular, semiconductor companies conduct research and development (R&D) on full wafer processing through the use of split lots, as the deposition systems are designed to support this processing scheme. This approach has resulted in high R&D costs and the inability to conduct extensive experimentation in a timely and cost effective manner.